Conventional techniques for precipitating particles from solution include methods in which a solution is heated in a container to evaporate off and remove the solvent and obtain particles (hereunder referred to a s “dry evaporation methods”), methods in which a solution is sprayed into hot air to evaporate the solvent in a gas phase, and precipitate particles as a dry powder (hereunder referred to as “spray dry methods”), and methods in which a solution of a solute dissolved in a good solvent is added dropwise to a heated poor solvent and the good solvent is evaporated off, to obtain a slurry of the particles and the poor solvent (hereunder referred to as “common methods using good solvent and poor solvent”).
A specific example of common methods using good solvent and poor solvent is described in Patent Document 1. Patent Document 1 discloses a method consisting of dropping a good solvent into a poor solvent heated to a temperature higher than the good solvent, wherein the difference between the boiling point of the good solvent and the heating temperature of the poor solvent is about 40° C.